Various cardiovascular procedures have been performed for many years typically by opening the sternum (referred to as a median sternotomy), and connecting the patient to cardiopulmonary bypass equipment to maintain the circulation of oxygenated blood throughout the patient's circulatory system. In this manner, the heart can be stopped and various surgical procedures performed such as coronary artery bypass grafting and replacement of aortic, mitro and other heart valves. Numerous other surgical procedures have been performed in a similar manner.
As taught by conventional techniques, cardiopulmonary bypass is established by a venous cannula introduced into a major vein such as the inferior vena cava, or into the heart itself, to withdraw deoxygenated blood from the patient and route it to a cardiopulmonary bypass (CPB) machine for oxygenation. Generally, an arterial cannula is introduced into a major artery such as the aorta, or a femoral artery, to deliver oxygenated blood from the cardiopulmonary bypass machine to the patient's arterial system.
In surgical procedures where cardiac function is arrested, the heart and coronary arteries must be isolated from the patient's arterial system. Using conventional techniques, the sternum is cut longitudinally, referred to as a median sternotomy, to provide access to the heart and other thoracic vessels. One method taught in the prior art, is to mechanically cross-clamp the ascending aorta downstream of the ostia of the coronary arteries, but upstream of the brachiocephalic artery, which will allow oxygenated blood from the cardiopulmonary bypass machine to reach the arms, neck, head, and the remainder of the body. A catheter can then be introduced into the ascending aorta between the cross-clamp and the aortic valve. Cardioplegic fluid is then infused through the catheter and into the coronary arteries.
One particular prior art device currently under development and disclosed in the literature, includes partitioning the patient's ascending aorta between the coronary ostia and the brachiocephalic artery to isolate the heart and coronary arteries from the remainder of the arterial system, arresting cardiac function, and introducing a balloon catheter through a femoral or other artery. More particularly, all blood flow through the ascending aorta is blocked by an inflatable balloon disposed on the distal end of a catheter which has been introduced through the femoral artery. The expandable balloon is positioned in the ascending aorta between the coronary ostia and the brachiocephalic artery so that it will block substantially all blood flow therethrough. The device includes a port at the proximal end of the catheter shaft for delivering cardioplegic fluid into the patient's ascending aorta upstream of the occluding means.
For the purposes of the present application, "downstream" means in the direction of normal blood flow through a blood vessel, i.e., further from the heart in the arterial system, and closer to the heart in the venous system. "Upstream" means in the direction opposite of the downstream direction. References herein to the "proximal" direction, means in the direction toward the end of the device that is closest to and held or manipulated by the physician, while "distal" means in the direction away from the user, and opposite the proximal direction.
The prior art devices also disclose means for providing cardiopulmonary bypass systems in which a bypass cannula is introduced into an artery (typically the femoral artery), and a blood flow lumen in the bypass cannula is connected to a lumen for delivering oxygenated blood into the patient's arterial system. A bypass cannula also can be positioned in a vein in the patient, and the blood flow lumen in the bypass cannula is connected to a means for receiving deoxygenated blood from the patient's venous system.
Generally, with the prior art devices, the aorta occluding device, generally a catheter having an inflatable balloon, is typically introduced transluminally, generally from a femoral vein or artery and advanced intraluminally into the ascending aorta. Due to various reasons, it may not always be possible to insert a catheter into the femoral artery or veins, thus making this prior art technique sometimes difficult or impossible to perform.
Improved methods and devices are therefore necessary to establish CPB which will eliminate the need to introduce catheters or cannulas through the femoral veins or arteries for the purpose of occluding the ascending aorta and for infusing cardioplegic fluid. The present invention provides alternative devices and methods which will accomplish the desired surgical procedure without the attendant risks and problems associated with the conventional procedures described.